JPH06241024A - Exhaust gas leakage detecting device of exhaust gas after-treatment device - Google Patents

Abstract

PURPOSE:To improve regeneration efficiency of a trap and exhaust emission control efficiency by improving reliability of an exhaust gas detecting device in an exhaust gas after-treatment device which captures particulates. CONSTITUTION:An exhaust gas leakage detecting device of an exhaust gas after-treatment device 1 which captures particulates in the exhaust gas consists of control valves 17A, 17B which cut off exhaust gas flown into the traps when traps 5A, 5B become in a recovery condition, the first temperature detecting means 22 which are formed on the upstream side in the flow direction of exhaust gas from the control valves, the second temperature detecting means 15A, 15B which is formed between the control valves 17A, 17B and the traps 5A, 5B, a control means 12 which reads detected information from the first and second temperature detecting devices at the time of trap recovery for a prescribed time and outputs a valve failure signal when detected information of the second temperature detecting means increases by a fixed amount according to detected information from the first temperature detecting means within the prescribed time, and a display means which indicates failure of the control valve from the valve failure signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas aftertreatment device for collecting particulates in exhaust gas discharged from a diesel engine, and more particularly to a control valve for regulating the amount of exhaust gas to a particulate trap. The present invention relates to an exhaust gas leak detection device.

[0002]

2. Description of the Related Art In the exhaust gas of a diesel engine,
Particulates containing carbon fine particles as the core are mixed in, and in order to collect these particulates without releasing them into the atmosphere, an exhaust gas aftertreatment device is provided on the exhaust gas flow path of the diesel engine. ing.

The exhaust gas after-treatment device is composed of a filter for collecting particulates and a heating device, and is arranged in each of the branched exhaust gas flow passages, and a certain amount of particulates is accumulated in the filter. Alternatively, the heating device is operated every predetermined time from the engine operation to burn the particulates to regenerate the trap portion. During regeneration of the trap section, a control valve provided in the exhaust gas flow passage is operated at appropriate times to prevent the exhaust gas from flowing into the trap section to be regenerated to perform regeneration processing, and the other trap section is exhausted. The gas is introduced to collect the particulates, and the durability of the trap is improved.

[0004]

By the way, in the above-mentioned exhaust gas aftertreatment device, the state of the control valve (valve leakage, defective operation, etc.) is detected by the pressure sensor in the pipe pressure in front of the trap portion, and the measured value is set. When the value exceeds the value, it is displayed as a failure of the control valve.

However, when the pressure is used as a parameter of the control valve failure, if the difference between the exhaust gas temperature in the front part of the trap section and the temperature in the trap is too large, the pressure cannot be detected due to the influence of the temperature, Alternatively, there is a problem that the absolute value is small even if it can be detected. If exhaust gas leakage cannot be detected in such a state, the amount of air in the trap during filter regeneration (when burning) will be excessive, leading to energy loss in the heating process of the heater, etc., and burning of particulates. There is a problem that leads to a decrease in efficiency, that is, filter regeneration efficiency.

[0006]

Therefore, an exhaust gas after-treatment device for collecting particulates in the exhaust gas by a trap portion arranged in the gas flow path of the exhaust gas discharged from the engine of the present invention is provided. The exhaust gas leakage detection device includes a control valve that shuts off the exhaust gas flowing to the trap portion when the trap portion is in a regenerating state, and an exhaust flow located upstream of the control valve with respect to the exhaust gas flow direction. A first temperature detecting means provided in the passage, a second temperature detecting means provided in an exhaust passage located between the control valve and the trap portion, the first and second temperatures during the trap regeneration When the detection information from the detection means is read for a predetermined time and the detection information of the second temperature detection means increases by a certain amount in response to the detection information from the first temperature detection means within the predetermined time, a valve failure occurs. Signal A control means for, and display means for displaying a failure of the control valve from the valve failure signal from said control means

[0007]

The temperature of the exhaust gas during engine operation is detected by the first temperature detection means provided upstream of the control valve in the flow direction of the exhaust gas, and the first temperature detection means is provided between the control valve and the trap portion. The temperature detecting means of 2 detects the exhaust gas temperature between the control valve and the trap during trap regeneration. The detection information detected by the first temperature detection means fluctuates up and down depending on the operating state of the engine, and the detection information detected by the second temperature detection means is exhausted to the location where the control valve is closed. The supply of gas is cut off, and it is cooled by the atmosphere and descends. At this time, when the control valve is open, the exhaust gas detected by the first temperature detection means is mixed with the exhaust gas detected by the second temperature detection means, and the detection information detected by the second temperature detection means rises. To do. The control means is
The exhaust gas temperature detected by the first and second temperature detecting means is read for a predetermined time during trap regeneration, and if the detection information detected by the second temperature detecting means increases by a certain amount within this time, the valve is opened. Then, the valve failure signal is output and the display means is operated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 indicates an exhaust gas aftertreatment device, and this exhaust gas aftertreatment device 1 is used for a diesel engine E (hereinafter referred to as “engine E”). A main exhaust pipe 3 that forms an exhaust flow path for exhaust gas discharged from the engine is connected to the exhaust manifold 2 of the engine E, and a primary muffler 4 is disposed in the main exhaust pipe 3. The main exhaust pipe 3 is a branch pipe 3 on the downstream side of the primafra 4.
Each of the tubes 3A and 3B is branched into A and 3B, and traps 5A and 5B for collecting particulates in exhaust gas flowing in the tubes are attached to the tubes 3A and 3B, respectively. The traps 5A and 5B here have the same configuration, and the configuration will be described using the trap 5A. It should be noted that the constituent elements of the trap 5B are illustrated by adding "B" to the reference numerals used in the trap portion 5A.

As shown in FIG. 2, the trap 5A has a particulate filter 8A (hereinafter referred to as "filter 8A") housed in an inflating portion 6Aa of a canister container 6A via a wire mesh 7A. In addition to this, an electric heater 9A, a heat reflection plate 10A, and an exhaust pressure sensor 11A are housed and supported in the expansion section 6Aa on the exhaust gas upstream side of the filter 8A. The exhaust pressure sensor 11A and the electric heater 9A are connected to the engine control unit 12 (hereinafter, referred to as "EC
U12 ”).

The electric heater 9A has a ribbon shape and, as shown in FIG. 1, an electromagnetic switch S connected to the ECU 12.
It is connected to the battery 13 via 1, S2, S3 and the starter switch S, and heat is generated during filter regeneration. The electric heater 9A is formed so as to be distributed substantially evenly in the exhaust gas flow passage cross-sectional direction, and quickly heats the generated heat energy by the heat reflection plate 10A and quickly collects the particulates collected by the filter 8A. .

As shown in FIG. 2, the filter 8A is made of a ceramic having a honeycomb structure in which a large number of narrow passages 14A are laminated in the same direction, and is particulate from exhaust gas passing through the side walls of the narrow passages 14A. Is configured to filter.

On the exhaust and branch pipes 3A, 3B located upstream of the traps 5A, 5B, an actuator 16 connected to an ECU 12 forming a part of an exhaust gas leak detection device.
Control valves 17A and 17B operated by A and 16B are arranged, respectively. The control valves 17A and 17B are normally open and are closed at appropriate times according to a drive signal output from the ECU 12 during trap regeneration.

The branch portion 30 between the main exhaust pipe 3A and the branch pipe 3B located upstream of the control valves 17A and 17B has an EC.
An exhaust gas temperature sensor 22 (hereinafter referred to as "exhaust temperature sensor 22") is arranged as a first temperature detecting means connected to U12, and detects the exhaust gas temperature near the branch portion 30 that changes according to the engine operating state. It is detected and sent to the ECU 12.

Traps 5A, 5B and control valves 17A, 17
In the exhaust pipe 3A and the branch pipe 3B located between B, an air introduction passage 21 connected to the air pump 20 is piped through valves 18 and 19 of the normally closed type, and an exhaust gas as a second temperature detecting means. Temperature sensors (hereinafter referred to as “exhaust temperature sensor”) 15A and 15B are provided, respectively.

The air pump 20 and the valves 18 and 19 are
It is connected to the ECU 12 and the ECU 12 is used when the filter is regenerated.
It is activated by the drive signal emitted from the. Pump 2
0 is connected to the ECU 12 via the switch S4.

The exhaust temperature sensors 15A and 15B are the trap 5
It detects the exhaust gas temperature between A and 5B and the control valves 17A and 17B, and sends the detection result to the ECU 12.

Here, the ECU 12 will be described. E
The CU 12 is an engine controller mainly composed of a microcomputer, is also a control means of an exhaust gas leak detection device, and is connected to the battery 13 via a starter switch S. Various information such as the engine speed, the engine load, the exhaust gas temperature Tn, and the exhaust pressure is fetched into the ECU 12, and various maps and programs defined by these are stored. In these maps, when the exhaust pressure in the canister containers 6A, 6B reaches a predetermined value, the filter 8A, 8B is in a regeneration mode, and when the exhaust pressure is less than a predetermined value, a collecting mode program or exhaust leak detection is performed. Routines etc. are also included.

In the regeneration mode, the filters 8A and 8B are alternately burned for regeneration, and in the collecting mode, the particulates in the exhaust gas are collected by the filters 8A and 8B. In the reproduction mode, the actuator 16A,
16B and electric heaters 9A and 9B as well as valves 18 and 19 and a pump 20 which sends drive signals to operate them.

The exhaust gas leak detection routine is performed by the temperature sensor 15.
A temperature gradient is calculated from the actual measurement value Tn that is the temperature information from A and 15B and the previous measurement value Tn-1, and control is performed depending on how many times the calculation result exceeds the value set in the ECU 12 within a predetermined time. Exhaust gas leaks from the valves 17A and 17B are detected, and when it is determined that there is an exhaust gas leak, a valve failure signal is output to the display means 23 connected to the ECU 12. The display means 23 is a warning light provided on the driver's seat or the like and blinks in response to a valve failure signal.

The operation of the exhaust gas aftertreatment device having such a configuration will be described. First, when the starter switch S is turned on, the engine E and the ECU 12 are activated, and the exhaust temperature sensor 15
The A, 15B, 22 and the exhaust pressure sensors 11A, 11B etc. are also activated, and the information from each sensor is taken in.

Exhaust gas discharged with the start of the engine passes from the main exhaust pipe 3 through the branch pipes 3A and 3B,
The particulates are collected by the filters 8A and 8B and discharged into the atmosphere. At this time, the canisters 6A and 6B
If the exhaust gas inside is not high, it is determined to be the collection mode, and the normal exhaust passage is secured to collect the particulates. Canister 6A with some particulates collected,
When the exhaust pressure in 6B reaches a predetermined value, the regeneration mode is determined and the regeneration mode is started.

In the regeneration mode, first, the actuator 16A moves to close the control valve 17A and close the trap 5
The supply of exhaust gas into A is cut off, and at the same time, the electromagnetic switch S1 is closed to energize the electric heater 9A and heat the filter 8A. When heated for a certain period of time, the air pump 20 is operated and the valve 18 is opened, the combustion air is supplied into the trap 5A, and the combustion (regeneration) of the filter 8A is performed.

When the trap 5A is regenerated, the trap 5B is regenerated, and the control valve 17B, the air pump 20, the valve 19 and the electric heater 9B are operated to regenerate the trap 5B.

Next, the operation of the exhaust gas leak detection device will be described with reference to FIG.
This will be described with reference to the flowchart shown in. Step a1
When it is not the regeneration mode, the counter set in the ECU 12 is cleared in step a2, the exhaust gas leak detection routine does not operate, and the collection mode is executed until the time comes. It

If it is in the regeneration mode, the operation proceeds to step a3, and the operation of the electric heater 9A on the trap side (here, the trap 5A) to be regenerated is confirmed. From sensor 15A to trap 5
The exhaust gas temperature Tn between A and the control valve 17A is taken in.

In step a5, the temperature data ΔTn of the exhaust gas located downstream of the control valve 17A is calculated by subtracting the temperature data Tn-1 acquired last time from the temperature data Tn acquired this time, and in step a6. Determine its orientation. That is, if the temperature gradient ΔTn is positive, it is determined that the temperature has risen, and the result is recorded in the counter set in the ECU 12 (step a7). Then, in step a8, the number of counts in step a7, that is, the number of temperature rises is compared with the set value (5), and if it is equal to or larger than the set value, the process proceeds to step a9 to output a failure signal and blink the alarm lamp. .

That is, when the control valve 17A is closed, the exhaust gas temperature Tn between the control valve 17 and the trap 5A is cut off from the supply of the exhaust gas having a high temperature, and the exhaust gas temperature Tn is cooled to the atmosphere. As indicated by the alternate long and short dash line, the temperature gradually decreases and ΔTn becomes negative.

However, if the control valve 17A is not closed,
The temperature data Tn penetrates into the exhaust gas on the upstream side of the control valve 17 shown by the solid line in FIG. 3, which changes the temperature depending on the operating state of the engine shown by the solid line in FIG. The temperature drops or rises as shown by the broken line in FIG. That is, when the control valve 17 is open, the temperature change causes the trap 5A and the temperature gradient ΔTn to be tilted in the positive direction. Therefore, by checking the temperature gradient ΔTn, a malfunction of the control valve 17 can be detected. it can.

[0029]

According to the present invention, the temperature gradient of the exhaust gas between the trap and the control valve is used as the parameter of the control valve, so that the trap before the trap is compared with the exhaust gas leak detection device using the pressure as the parameter. It is possible to reliably detect the failure of the control valve without being affected by the exhaust gas temperature of the section or the temperature in the trap. As a result, since the control valve and the like can be quickly repaired, the invasion of exhaust gas into the trap at the time of regeneration can be immediately prevented, and the particulate combustion efficiency, that is, the filter regeneration efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exhaust gas post-treatment device that employs an exhaust gas leak detection device that is an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a particulate trap portion.

FIG. 3 is a characteristic diagram of an exhaust gas temperature corresponding to an operating state of a control valve.

FIG. 4 is a flow chart showing control of an exhaust gas leak detection device that is an embodiment of the present invention.

[Explanation of symbols]

 1 Exhaust Gas Aftertreatment Device 3, 3A, 3B Exhaust Gas Gas Flow Path 5A, 5B Trap 12 Control Means 15A, 15B Second Temperature Detecting Means 17A, 17B Control Valve 22 First Temperature Detecting Means 23 Display Means E Diesel Engine 12,15 (A, B), 17 (A, B), 22,23 Exhaust gas leak detector

Claims (1)

[Claims] 1. An exhaust gas leak detection device in an exhaust gas post-treatment device for collecting particulates in the exhaust gas by a trap arranged in a gas flow path of exhaust gas discharged from an engine, wherein the trap is provided. A control valve for shutting off the exhaust gas flowing to the trap when the exhaust gas is in a regeneration state, and a first temperature detecting means provided in the exhaust flow passage located upstream of the control valve in the exhaust gas flow direction. A second temperature detecting means provided in an exhaust passage located between the control valve and the trap portion, and reading detection information from the first and second temperature detecting means for a predetermined time during the trap regeneration, Control means for outputting a valve failure signal when the detection information of the second temperature detection means increases by a certain amount in response to the detection information from the first temperature detection means within the predetermined time; Exhaust gas leakage detection device of an exhaust gas post-processing apparatus and a display means for the valve fault signal from the means for displaying a failure of the control valve.